1. Field of the Invention
This invention relates generally to a recording and reproducing apparatus, and more particularly to an apparatus of the kind which records and reproduces a variety of data by the use of a recording medium having a large capacity such as a magneto-optical disk.
2. Description of the Prior Art
Conventionally, hard disk units are known which can write data on a large capacity disk unit for information storage.
This unit is generally used as data storage for a computer. The information is recorded in a concentric or spiral track formed on the disk and the disk is rotated at a predetermined rotational speed.
FIG. 1 is a block diagram schematically showing a prior art recording and reproducing apparatus. Writing data in and reproducing the same data from a hard disk unit 1 is effected by a CPU 3 through a data bus 2. The disk arranged in the hard disk unit is rotated at a constant rotational speed irrespective of (not synchronized with) the transmission rate of data inputted on the disk. Instead, the rotational speed is timed by the CPU 3 for recording data on the disk. The data processed by the hard disk unit may thus be non-sequential data.
Data communication between the hard disk unit 1 and the CPU 3 is effected via a RAM 4 which serves as a buffer memory. It is further possible to communicate the data between the RAM 4 and the hard disk unit 1 at a high speed by the use of a DMA controller, without interruption by the CPU 3, wherein data is processed non-sequentially.
Data representing a still image or the like can be processed as a one frame portion of intermittent data by using a frame memory for the RAM 4.
FIG. 2 is a block diagram showing a construction of a circuit for processing such burst data. Disk controller 5 is arranged between the CPU 3 and the disk unit 1. A required portion of burst data stored in RAM 4 is recorded in the disk unit 1 through the disk controller 5 under the control of the CPU 3. This construction is used, for example, in an electronic mail system.
The "new media era" provides us with a variety of information in many kinds of media, that is, multi-media information. Such information includes non-sequential or intermittent data which does not have any correlation with adjacent data, such as computer data; data which has a correlation with adjacent data, but is as a whole non-sequential, such as data representing a still image; data which has a correlation with adjacent data and is sequential, such as digital audio data; and so on. These data have different characteristics from each other.
It would be useful to be able to write all the types of data information on a disk and provide users with the disk. The magneto-optical disk is a rewritable large capacity storage medium and can store multi-media information. The magneto-optical disk is different from a hard disk unit which records and reproduces data under strictly controlled conditions because it produces errors at a higher ratio than the hard disk unit. Thus the data stored in the magneto-optical disk is provided with redundant bits for error correction codes and other functions for detecting and correcting errors.
However, while the error correction is effective with respect to random errors, it is not so effective with respect to burst errors. It may be better to treat data including errors as defective rather than correcting the errors where computer data is concerned. On the other hand, it is sufficient to correct errors in data forms like PCM audio data to such a degree that the errors cannot be audible. Errors in such data which cannot be corrected can be interpolated by the use of adjacent data having a correlation with erroneous data so that the errors will not be conspicuous.
Even so, if data is recorded in the same order as the original data and a burst error occurs in a portion of that data, then that data portion can no longer be interpolated.